In a manufacturing site such as a factory, a communication system is configured by connecting field apparatuses such as a PLC (Programmable Logic Controller), an inverter, and a thermometer. Various kinds of processing are performed while data communication is performed among the field apparatuses. In such a communication system, to guarantee a real-time property of the data communication performed among the field apparatuses, a token passing system employing a LAN (Local Area Network) standard of an Ethernet (registered trademark) technology or the like is adopted. However, in the communication system in which the field apparatuses are connected, data transferred among the field apparatuses tend to be affected by noise. Therefore, in the communication system in which the data communication is performed among the field apparatuses, it is desired to improve noise resistance and efficiently transmit data.
For example, in a data communication control system disclosed in Patent Document 1, frame length used for data transfer is set short. When a bit error occurs in a data transfer frame, a short frame in which the bit error occurs is retransmitted. This makes it possible to suppress a data amount to be retransmitted and improve efficiency of the data transfer.
Patent Document 1: Japanese Patent Application Laid-Open No. H09-160851